Electric furnace for the continuous extraction of zinc from its ores.



E. P. 06TH L P. R. PIBRRON. ELECTRIC FURNACE FOR THB CONTIN 30C. EXTRAGTION 0F ZINC PROM ITS CRES.

APPLIGA'TION nz-D AUG. 13, 1908.

Patented Jan. 3,1911.

3 'SHEETS-SHEET 1.

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E. F. 06TH @L P. H. PIBRRON.

T1015 OP ZINC FROM ITS ORBS.

APPLICATloh' YIIEI.1AUG.1.=.1905.

Patented Jan. 3, 1911.

ELECTRIC PURNAGE PGR THE G01-:muws 980,763.

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(Isl III E, P. CTE a I. R. PIERRON ELECTRIC FURNACE FOR THE CONTINUOUS EXTRAGTION OP ZINC FROM ITS GRES.

APPLICATION FILED AUG. 1s, 1908.

onirico srnrns PATENT EUGENE rRANcois corri AND PAUL RAMBERT rIERnoN, or LYON, FRAME ELEQTIRIC FURNACE FOR THE CONTINUOUS EXTRACTION 0.F ZINC FROM ITS CRES.

Specification of Letters Patent. Patented Jan. 3, 1911.

Application tiled August 1in, 1908. Serial No. 448,411.

the operationsand to the diculty f con- 5 5 I To all 'wh/)m 'it'may concern:

Be it known that we, EiciaNi-i FnANgois densing the zinc carried along into'a current i CTE, of 24: Rue Sully, electrical engineer, of carbonio oXid. Y

i and PAUL RAMnlrr Premio-N, of l Rue dAl- The electric furnace has already been ap- 5 grie, electrical engineer, both of -Lyon, plied to the roastin land. reducing process,

Rhne, Republic of France, have invented which has improv this process purti'cu- 60 y an Electric Furnace for the Continuous Exlarly in what concerns the utilization ofthe traction of Zinc from lts Orcs, of which the heating energy. l3nt, even in this case, the

-L following is n. full, clear, and cxact'dcscripcontinuity of the operations can be scarcely 1o tion. obtained on accountof the dtilculty to evacl Up to the present time, it has not been nate by melting thel exhausted charges.-65

ossible to simultaneously realize the three Furthermore, Athis method sliovy' 'the Same important conditions upon which the disadvantage as in the. treatin-by coal to economy of the zinc metallurgy by the dry effect the condensation of the inclina curl5 process is based, and which are as follows: rent of carbonio oxid. the Weste-"of zinc 1st complete condensation of the metal; 2nd 1 is more considerable .'11I the ceso ofelec- 70 utilization of `the Whole heating power suptric furnace than in ,llcll 'Qf tlv-@Q11 plied; 3rd continuous distillation of the zinc. nace because then the condenser is diilicultly Considering, for example, the case in maintained in the ,"'1i mits"of temperature which blendes are to be treated,two methods within which a 'good condensation of the of treatment exist, as is Well known. zinc can be obtaine 'f 75 'The one process, the so-called roasting and The presentinvnton 1213565 t0 @n elec`r reducing process, consists in roasting the tric furnace in which the -zinc ore ig trein-,ed ore so as to convert the sulfid into' oxid by the so called precipitating PI'OOGSS no* l which is then reduced by coal'; the other one cording to which the Zinc iS dpld by n I called precipitating process, consists in rethe iron, thereby "allo/wing to realize the 80 moving directly the zinc from its sulfid by three essential conditions as above mentioned.

a common metal, .such as iron. A ln fact, the treatment in the new fur*A AHerctofore, the roasting und` reducing j nace combined with the great thermic 0utprocess was the only one used.v In fact, acl put the advantages of the continuity ofthe Acording to the precipitating process, the l process and of the condensation of zinc in 86 melting of the blende with iron must be cfl the absence .of carbonio oxid. The operation- ,l fected in a closed vessel.- The retorts conr can be, continuous whereas the iron sulfid taining the-reactive mixture must have thick being very fusible may be eliminated at 1 35 walls, whereas these walls are attacked by same 'timeas thc slugs which have been renthe slugs which are formelL/and also by the dared, fusible by the addition of suitable 90 iron sultid; it results in a. bad utilization fluxes. The exhaust of 'the betches can of the heat which is transmitted to thein--JQtl1oicfore be effected in a continuous manner tcrior of the retorts only withdiiticulty.' ln and without causing nir to reenter the fur- 40 order that the heating power should not bc nace. lhe charges may bc introduced in u too greatly reduced, there has arisen n cuscontinuous manner also without cuuSkin air 95 tom of giving to these retin-ts small sizes to reenter. On the other hand, the v'oatiland'to increase their number, which menus u ized zinc reaches the'condcncl in the'iabcomplication oi the furnace :rnd a liscon sence of any other gaseous product and continuity in the operations. Finally, the lensesitsclf more completely. F uriihtmOre,

treatment of the iron ysullid wus not pracas the zinc is displaced `from its Sulfid with 100 tical with the known n'ugtnllurgimil procout any great expense of power, it Willbe ceses. Therefore, the precipitating process seen that the three advantages of the con- 1was inapplicable with the coul furnaces. tinuous operation, ofthe economy and'of the Accordingly the roasting and reducing complete condensation of the zinc are 0bmethod. was usc-d. T his method however tained. It is further to be observed that 'one 105 has various disadvantages essentially due to may in this way treat directly oor blendes thc had transmission of heat through the which it was necessarydto enric i before the walls of the rctorts to the discontinuity of trcntn'ient with the o processes. On the is easy to treat.

'surrounded with a thiclg lining of fire-bricks crude blendc by the iron, there is in fact an g' eso other hand, as electric power is available it the sultidot iron in order to recover iron.

A very in'i'iortant point is that of the condensation of the zinc vapors in the con denser. [t is well known that condensation takes place only between the two limits of 430 and 5G00 C. Above 560, there is no condensation; beneath 4300, the zinc will condense into powder. lltl is therefore nec cssary to maintain the condenser between these two limits of temperature. However, in the resent case, in which the treatment'is eifecte in the electric furnace, the radiation of the furnace cannot be relied upon as is the case with coal furnaces, nor upon the heat emitted by the gases generated in ther furnace, in order to maintain the condenser at a suitabler temperature. For the purpose of regulating at will and under the best conditions, the temperature of the condenser, the same is rovided with a special electric heating appliance enabling the operator to regulate at will the temperature and to obtain furthermore different temperatures in the several arts of the condenser. Thisdevice bis 'pre crably constituted by a heating column arran edin the axis of the condenser and traverse by an electric current which heats the same by the Joule etl'ect this column may comprise arts of unequal electric resistance which, ieats morelor less the several parts of the condenser.

The invention also comprises a device by means of which in case at the same time zinc vapor, zinc oxid, would be evolved from the furnace, `which zinc oxid would be formed either by the presence ot' steam, or by carbonic acid introduced with the charges of ore, the metallic vapors would pass before entering into the condenser over a column of coal rendered incandescent by thev passage of the electric current. U nder` these conditions, the oxidized met-al is reduced and only zinc vapors and a little carboiiic oxid enter the condenser.

The accompanying drawing shows by wayn of example several forms of construction of the new electric furnace.

Figure 1 is a vertical section of the new furnace. Figs. 2 and 3 show a 'modified forni in vertical section and in elevation.

As represented, the furnace is essentially constituted by a channel-shaped retort or acircular channel a covered with an arch and located in' a metal armature which is of a cylindrical shape and can be taken to pieces. It operates exclusively as a resistance turnace.. In the c c of the treatment of the advantage in elliccting the. melting oi' the oi sulids which soil the distilled zinc and complicate its puritication is thereby avoided.

The current is led into thecrucible through electrodes one of which is represented at formed each by block of graphite carbons located in the brickwork.

rlhe drawing shows afurnace operating with a three phase current and comprising consequently three similar electrodes; the

thc resisting conductor receiving the three phases of the current. The bottom of the Crucible is slightly inclined toward the taphole d. The charge introduced at c melts and passes through thc crucible in running toward this outlet.

. The metallic vapors issuing from a are obliged to traverse the column of incandescent coal e to get into the condense: f ar ranged in the axis of the furnace. The dis tillation thus takes place per desee/naam in the direction of the arrows.

The axis of the condenser which is a wide cylindrical tube is occupied by a column g of refractory materials filled with coal or graphite dust which is .inoie conipressedatthe top than at the bottom', so as to constitute a somewhat resisting electric conductor which becomes heated a little more at the bottom than at the top; the current reaches this column and leaves it through suit-ably arranged graphite blocks. After having traversed it as well as the caibons c maintained in an incandescent state by a suitable adjustment, the electric current leaves this apparatus through an electrode i passing down along the axis of a closed hopper arranged over the vault of the furnace and containing a coal supply for several days work. As the combustion which is very slow proceeds, this'coal descends at e and the ashes fall down to the bottom of the condenser.

The system of electric resistances formed by c. (f. /t is put in circuit dver a transformer ot varying connections so as to fulfil conveniently and at will the conditions of voltage and amperage which are required to ob* tain the suitable effects of temperature. The electrode It can'be maintained immovable during the operation; it is lowered for the purpose of taking up wear only when the Stoppers of the hopper are removed to supply the latter again.

The mechanism for the continuous introduction ot charges consists in ay smell :a tal spattlc -z keyed upon an lifiairfor'Y tf and rotating in a closcd `tram with a play .between it and the walls ot' this li-ani; this drinn communicates on the. one hand with the loading oriice of tir-.r furnace and, on the other hand, with nn hopper in 'which an elevator, not` shown, throws over thc charges. The ore 'forms above the critico matter melting in the circular vat a 'forms 980,76; A p a c a talus or slope in which thc spattle i 'dips at every revolution to take a certain quantity which is inmiediately inished into this orifice. A small electric motor /c causes the spattle i torotate. The delivery of this loadiner or charging apparatus is regulated at will` sinnlltaneously by the rotary speed of the spattle and by a small sliding valve which can be moved vertically in tront'ot' the hole connecting thc hopper with the drinn, thereby controlling quantities ot' charges taken ott by the spattle. The apparatus. th-us .constituted is simple. very strong, readily `adjustable and capable of continuously charging the furnace without causing any air to reenter.

It is important that provision b e made for continuously tapping cti the sultid. of iron and the slags. To this purpose. the furnace comprises an electrode l which projects into the tap; h olc arranged as a siphon in the thickness of. the furnace wall, This electrode is connected with 7) and the intensity of the currentv passing through the same and required for maintaining the sulfid of iron and the lSlgS in a very tluid state in the orifice d and the sphon is regulated according to the working of the furnace by a suitable combination of the electric current generating a'lpparatuses.l

While the sultd of ironis run ott, sulfurous acid is formed in contact with 'air and zinc oxid fumes resulting from the withdrawal by the slags of small quantities of free and nondistilled zinc are produced. To get rid of these gses and fumes which are a source of great trouble for the wol-lonen. the tapping nozzle is caused to open in a chest in connection with a cast. iron pipe 0 through which the molten matters coming out of. the furnace'axially fall. A strong draft generated by a fen arranged at the bottom of this 'pipe exhausts in the. direction ofthe arrows the sulfurous gases and the zinc voxid fumes to directthem' into absorpw tion shafts.

.In order to avoid tbc very painful labor consist-ingl in removing from the furnace" room the sulfid of iron and the int'eandescent slags, the mass of molten material fiowing in a stream axially of the pipe o falls upon a powerful water spray directed .by a nozzle i]- along the 'inclind bottoni -p ota closed channel arranged beneath the pipe o. 'lhc sulfid of iron and the slags are thus reduced into rough sands carried along by the water stri-.ani'into decantation tanks. The evolved steam is exhausted hy the drat't.

The furnace is completed by a sheet. iron bell v* in which the lower part ot' the condenser f projects. The zinc vapors which esca c from the condenser settle themselves in tie form of dusts in this vat. the rover of which can be easily dismounted.

The distilled zinc falls into a receptacle s .proiided with a long channel leading the tiilid metal outwardly.

The current cornes to. the electrodes b through the barsu, the supporting columns of l the furnace. and the conductors t.

1t is to be observed that the adopted arrangements have for ettect to utilize the whole of the heatproduced by the furnace in maintaining the condenser in a hot state, so as to reduce as much as possible the quantity of current used for heating this appa ratns. This furnace being tight closing at the. saine time does away withvv the readmisv sion ot' airA and the production of fumes which are dangerous for the workmen.

In the foregoing, the furnace has been U considered as. being fed by an alternating current.l The same may also be fed 'by di` recti current. However, it mustbe observed that this furnace is particularly well adapted for the utilization of three phase currents working in resistance by Athe fact that the molten material forms a ring conneet-ing the three electrodes in presenting between-each of them pieces of conductors which have very approximately thc same re# sistance and avoiding the difference of phase. Figs. 2 and 3 show another arrangement in which the furnace comprises a cylin-Y drical cruc'ibl'e of refractory and insulating materials: magnesia, chalk', dolomite, etc.. with an inner lining 71, of carborundu'u or chromite, the whole lbeing contained in a sheet-iron vat. b., This 'crucible is provided at its center with a protuberance c so that it has the terni of the bottom of a bottle; electric conductors'insulated from all the other parts ofthe apparatus terminated by prongs embedded in carborundum or chromitc `connecting the erucible with one pole of the circuit. The arch or vault is formed by a movable cover d made of the same materials as those forming the exterior of the vat a. .The other pole of the furnace. is

can be vertically displaced by hand or me` p chanically and which. centrally traverses the arch. All the joints between this cover and the vat, ou the one hand, and the electrode. ontlie other hand, are made tight b v a layer of powdered refractory materials packed upon these joints.

The charges (formed of the mixture of ore, of minute grains, of iron or cast iron and of fluxes) arcfintroduced in a continuous and adjustable manner into the crucible by an orifice through thc vault near the point ot the electrode e by n'ieans ot' a distributing mechanism f (Fig. 3). rl `he tappings or rnnnings ot' sulrid of iron and ot slags are eifel-ted through an orifice leading` to an external channel g.

The lining of the rrueiblwith ehromite or earborumlum is donc t'or the following reasons: lhe refractory materials such as sav magnesio, lime, bauxite, dolomite, alul to the condenser ,5^ formed of a large vermina, etc., in addition to that they forni fusible silicates with the. gnngue of the oro are more or less soluble in the salud of iron therefore they cannot. be umd. (ln 'the other4 give in contact with iron very fluid castv irons which in virtui.-A of iis great density instantaneously falls io the bottoni of r`the Crucible under the hed o't' iron sullid so that some of the iron esca i flint; reaction'tipon the blende and the. walls of the Crucible are quickly attacked. 0n the other'hand, as it is necessary to mold the Crucible of a single piece and of a single material in the whole art which should contain the molten '-baths, in order to avoid the dislocations due to inequalities of expansion between dill`erent materials and so, furthermore the refractory material used. must be electrically conductive, carborundum or chromite is used. Of course, the lining can' consist of any other material which will be capable of resisting temperatures of from '1600" to 180()o in the presence of silica, of iron and of sulfid of iron, while offering an electrical resistance of substantially the same magni-l tude, as that of carborundum.

The special arrangement of the bottom,

of the crucible gives a very important resuit: The Whole of the interior of the crucble being conductive, if the bottom was of the usual shape, the electric current su pplied from the electrode e to the center of the surface oil the molten bath would pass to the walls in'radiating through the upper layers and then the heating o the bath and 'of the walls` would not be correctly effected.

It is advisable to direct the flow of current through the batches s o as to melt saine according to a core in the axis of the Crucible.

i This result isobtained with the protuberchannel ii.'

ance c bringingr to `a maximum the density of the current in the region ot' the dotted lines represented Fig. l and which is the most conductive by the fact that ithas the highestteiiipei'atur. ln this way also, the walls are always maintained at a tr-.inperiturc which is more uniform and somewhat lower than that of their fusion temperature so as to insure the good preservation thereof. Finally. the sulfid ot iron which when formed has no longer to receive the heat and must. only be maintained fluid has not to undergo here the action of the current.

and therefore the clectrotherinical `yieldingis inn'n'f'ivcd. The furnace works al saine timel by resistance and with an are. because while thc p oint ot the electrode if does not come in contact with iu which thil arc rodnt-ed being4 rendered conductive in' thxl metalli/.z vapors.

IThe volatilizcd '/.ino p sst-s through the over a laver of incainlcsccni coal i which it must traverse before coming tl butin the interval i l l l l tical cylinder 1 of sheet iron having an inner lining of refractorv earth. The coal is introduced at #through the hollow electrode Z. The electric current passes through this coal., bringing same to incandescence and passes out through the electrode m which is in the axis of the condenser, the system being branched in series upon a transformer o' varying connections. -The resistance of the column m is such that this conductor will be bron htto red heat and will maintain the wal s of the condenser at a suitable temperature.

The composition of the electrode m is such that its resistance is not. uniform over its whole length but greater at the bottoni than at the top so as to exactly distribute the heating according tothe requirements of the condenser.

The coal ashes pass with the zinc vapors through orifices a provided between teeth -forniing a grate and Vmaintaining the conmaintained in a fluid state by the heating of i the electrode establishes the passage of the current from the latter to the conductors.

The passage of the metallic vapors through the layer of incandescent coal i' has or effect to reduce the oxid of zinc which might have been formed, so that in the condenser only arrive zinc vapors in an atmosphere of carbonio The metal running over the walls of the condenser contains some impurities formed of silica.l iron and metals alloyed with zinc in the blonde; vit is necessary to submit it to a rchning melting so as to deprive it therefrom. For this purpose, the metal is received according to its condensation in the vat o in which it is maintained in a fluid state during a sutiicient time under the heating action of the electric current passing through the'same. The scums ascend to the surface of the bath in which the -are -inixcd with coal ashes coming from 'i and are discharged in the wide closed space surrounding the vat o and from which they are withdrawn from time to time through suitably arranged orifices.

Coinrnercially pure 'zinc is drawn off by the pipe p.

li Gf .introduction cf charges eration. The duets are deposited upon the bottom of the bell g from which they are emptied through. doors rc". 1ihe above indicated mechanism 'for the is composed of a metallic hopper {IJ-lig.. 8) with plane Walls, the one otrvhich is vertical, Secured upon e the furnace and at the bottoni ci i horizont-al disk fr oi steel r i Sonie 'radial ribs. gh an opening provided ical 'wail of the hopper and through i the Vone lfurnis a 'slope Which'ends through enchannel at the inlet orifice s provided in vthe vault of' the furnace near the electrode c. n, hinged shutter WQ i,oints closes, in following the inciination ot the slope, the top of thechannel containing the This dislt er" is pivot-ally sus Bonded at the top and its rotary motion is controlied 'by a tangential gearing if and a nulley a. In turning vat Aa greater. or smaller speed, the disk a. causes a greater or smaller quantity crore to slide into the furnace per unit of time.' This device is thereby, characterized that-.it has no delicate part heated by the Contact with .zinc vapors, that it has no deadspace in .which powder may form itself, so as to ailoiv itsrapid clearing in case of cldgging.

The condensernced not necessarily have the forni of a vertical cylinder nor be heated 'by the Joule eifectgit can for instance he ct an ovoid internal shape and .heated by the radiation of an electric arc placed near one of the foci of this capacity. The essential point is 'that it can be electrically heated by a device permitting to regulate its tempera ture at will and according to `the operatic of the furnace.

lhe above'arrangelnents have been given by Way of example only; the forms, dimensions and. detail arrangements may vary in of the inventidn. t

Claims:

l, In an electric `furnace of the character specitied, a cioeed retort of annular `forni, a protuherance at the center of the bottom ci the retort, two oppositely arranged electrodes placed in the axis of the' retort, a condenser in connection with the retort and formed by a 'vertical cylinder in which is arran ed an electrode.

2., n an electric furnace of the character specified, a closed annular retort, a condenserv formed by 'a vertical cylinder arall cases 'Without modifying the 4principle ranged in theiaxis of the furnace, an upper l This disk' th tight.

electrode formed by a block of graphite far-- ranged inthe axis of the retort, and a lower electrode placed at the center 'of the con-- denser. i

5:1, ln an electric furnace ci. the character speciied, a closed annular retort, a ,com

denser formed by a vertical cylinder arthe retort, two oppositely arranged elec# trodes placed in the axis of the retort, acondenser; in'connection with the retort and formed by a vertical cylinder in.which is arranged a resistance element, a tap-hole for the retort, and a water s ray below .the taphole and on to which mo ten metal from the retort falls,

5, In 'an electric furnace of the character specified', a closed yretort of annular form,`a protuberance at the center of the bottom of the retort, two o positely arranged electrodes placed-in te vaxis of the retort, a condenser formed by a vertical cylinder in which is arranged an electrode, a ta hole, a Water spray below the tap-hole an on to which. molten metal from the retort falla' and means for feeding the furnace. l y

(i. ln an electric furnace of the character specified, a channel shaped retort circular in forni, a condenser in the axis of the'retort, a pair 'of oppositely arranged electrodes in the condenser, a tapholeat one side of the ously rotating shaft provided with .a lateral- Wing or blade, and an inclined chute for the material, said shaft being arranged at the outlet of the' chute.' Y

The foregoing specification of our electric furnace :for the ceafitinuousl extraction of zinc 'from its etienne renuncie corn.

PAUL RAB/[BERT PERRQN.

Witnesses:

' Enorme N..- BnowNn,

' Manin VAcHoN.

ores, signed by us this 29th day of July i908. f v Y 

